Uplink procedures for LTE/LTE-A communication systems with unlicensed spectrum

ABSTRACT

Long term evolution (LTE)/LTE-Advanced (LTE-A) deployments with unlicensed spectrum leverage more efficient LTE communication aspects over unlicensed spectrum, such as over WIFI radio access technology. In order to accommodate such communications, various uplink procedures may be modified in order to handle communications between licensed and unlicensed spectrum with LTE/LTE-A deployments with unlicensed spectrum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/866,925, entitled, “UPLINK PROCEDURES FOR LTE-UCOMMUNICATION SYSTEMS”, filed on Aug. 16, 2013, which is expresslyincorporated by reference herein in its entirety.

BACKGROUND

Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to uplink procedures forlong term evolution (LTE)/LTE-Advanced (LTE-A) communication systemswith unlicensed spectrum.

Background

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, and the like. These wireless networks may be multiple-accessnetworks capable of supporting multiple users by sharing the availablenetwork resources. Such networks, which are usually multiple accessnetworks, support communications for multiple users by sharing theavailable network resources. One example of such a network is theUniversal Terrestrial Radio Access Network (UTRAN). The UTRAN is theradio access network (RAN) defined as a part of the Universal MobileTelecommunications System (UMTS), a third generation (3G) mobile phonetechnology supported by the 3rd Generation Partnership Project (3GPP).Examples of multiple-access network formats include Code DivisionMultiple Access (CDMA) networks, Time Division Multiple Access (TDMA)networks, Frequency Division Multiple Access (FDMA) networks, OrthogonalFDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.

A wireless communication network may include a number of base stationsor node Bs that can support communication for a number of userequipments (UEs). A UE may communicate with a base station via downlinkand uplink. The downlink (or forward link) refers to the communicationlink from the base station to the UE, and the uplink (or reverse link)refers to the communication link from the UE to the base station.

A base station may transmit data and control information on the downlinkto a UE and/or may receive data and control information on the uplinkfrom the UE. On the downlink, a transmission from the base station mayencounter interference due to transmissions from neighbor base stationsor from other wireless radio frequency (RF) transmitters. On the uplink,a transmission from the UE may encounter interference from uplinktransmissions of other UEs communicating with the neighbor base stationsor from other wireless RF transmitters. This interference may degradeperformance on both the downlink and uplink.

As the demand for mobile broadband access continues to increase, thepossibilities of interference and congested networks grows with more UEsaccessing the long-range wireless communication networks and moreshort-range wireless systems being deployed in communities. Research anddevelopment continue to advance the UMTS technologies not only to meetthe growing demand for mobile broadband access, but to advance andenhance the user experience with mobile communications.

SUMMARY

In one aspect of the disclosure, a method of wireless communicationincludes generating, at a UE, one or more uplink signals fortransmission to a serving base station, wherein the UE is configured totransmit communication signals to the serving base station over at leastunlicensed spectrum and receive communication signals from the servingbase station, determining, by the UE, a non-clear channel assessment(non-CCA) subframe for transmission of at least one of the one or moreuplink signals, and transmitting, by the UE over an unlicensed band, theat least one of the one or more uplink signals in the non-CCA subframe.

In an additional aspect of the disclosure, a method of wirelesscommunication includes identifying, by a serving base station configuredfor communication over at least unlicensed spectrum, a non-CCA subframefor reception of at least one uplink signal, and receiving, at theserving base station, over an unlicensed band one or more uplink signalsfrom a UE in the non-CCA subframe.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes at least one processor and a memorycoupled to the at least one processor. The at least one processor isconfigured to generate, at a UE, one or more uplink signals fortransmission to a serving base station, wherein the UE is configured totransmit communication signals to the serving base station over at leastan unlicensed spectrum and receive communication signals from theserving base station. The at least one processor is additionallyconfigured to determine, by the UE, a non-CCA subframe for transmissionof at least one of the one or more uplink signals. The at least oneprocessor is also configured to transmit, by the UE over an unlicensedband, the at least one of the one or more uplink signals in the non-CCAsubframe.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes at least one processor and a memorycoupled to the at least one processor. The at least one processor isconfigured to identify, by a serving base station configured forcommunication over at least unlicensed spectrum, a non-CCA subframe forreception of at least one uplink signal. The at least one processor isadditionally configured to receive, at the serving base station, over anunlicensed band one or more uplink signals from a UE in the non-CCAsubframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram that illustrates an example of a wirelesscommunications system according to various embodiments.

FIG. 2A shows a diagram that illustrates examples of deploymentscenarios for using LTE in an unlicensed spectrum according to variousembodiments.

FIG. 2B shows a diagram that illustrates another example of a deploymentscenario for using LTE in an unlicensed spectrum according to variousembodiments.

FIG. 3 shows a diagram that illustrates an example of carrieraggregation when using LTE concurrently in licensed and unlicensedspectrum according to various embodiments.

FIG. 4 is a block diagram conceptually illustrating a design of a basestation/eNB and a UE configured according to one aspect of the presentdisclosure.

FIG. 5 is a block diagram illustrating a transmission timeline for anLTE/LTE-A deployment with unlicensed spectrum configured according toone aspect of the present disclosure.

FIG. 6 is a block diagram illustrating a transmission timeline in anLTE/LTE-A deployment with unlicensed spectrum configured according toone aspect of the present disclosure.

FIG. 7 is a block diagram illustrating a system bandwidth of anLTE/LTE-A deployment with unlicensed spectrum configured according toone aspect of the present disclosure.

FIGS. 8A and 8B are functional block diagrams illustrating exampleblocks executed to implement one aspect of the present disclosure.

FIG. 9 is a block diagram illustrating a transmission timeline in anLTE/LTE-A communication system with unlicensed spectrum configuredaccording to one aspect of the present disclosure.

FIG. 10 is a block diagram illustrating a transmission timeline of anLTE/LTE-A UE with unlicensed spectrum configured according to one aspectof the present disclosure.

FIG. 11A is a call flow diagram illustrating a call flow in an LTE/LTE-Acommunication system with unlicensed spectrum between an eNB and UEconfigured according to one aspect of the present disclosure.

FIG. 11B is a call flow diagram illustrating a call flow in an LTE/LTE-Acommunication system with unlicensed spectrum between the eNB and UE,configure according to one aspect of the present disclosure.

FIG. 12 is a block diagram illustrating a combined random accessresponse message from a base station configured according to one aspectof the present disclosure.

FIGS. 13A and 13B are functional block diagrams illustrating exampleblocks executed to implement one aspect of the present disclosure.

FIGS. 14A and 14B are functional block diagrams illustrating exampleblocks executed to implement one aspect of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to limit the scope of the disclosure.Rather, the detailed description includes specific details for thepurpose of providing a thorough understanding of the inventive subjectmatter. It will be apparent to those skilled in the art that thesespecific details are not required in every case and that, in someinstances, well-known structures and components are shown in blockdiagram form for clarity of presentation.

Operators have so far looked at WiFi as the primary mechanism to useunlicensed spectrum to relieve ever increasing levels of congestion incellular networks. However, a new carrier type (NCT) based on LTE/LTE-Ain an unlicensed spectrum may be compatible with carrier-grade WiFi,making LTE/LTE-A with unlicensed spectrum an alternative to WiFi.LTE/LTE-A with unlicensed spectrum may leverage LTE concepts and mayintroduce some modifications to physical layer (PHY) and media accesscontrol (MAC) aspects of the network or network devices to provideefficient operation in the unlicensed spectrum and to meet regulatoryrequirements. The unlicensed spectrum may range from 600 Megahertz (MHz)to 6 Gigahertz (GHz), for example. In some scenarios, LTE/LTE-A withunlicensed spectrum may perform significantly better than WiFi. Forexample, an all LTE/LTE-A deployment with unlicensed spectrum (forsingle or multiple operators) compared to an all WiFi deployment, orwhen there are dense small cell deployments, LTE/LTE-A with unlicensedspectrum may perform significantly better than WiFi. LTE/LTE-A withunlicensed spectrum may perform better than WiFi in other scenarios suchas when LTE/LTE-A with unlicensed spectrum is mixed with WiFi (forsingle or multiple operators).

For a single service provider (SP), an LTE/LTE-A network on anunlicensed spectrum may be configured to be synchronous with a LTEnetwork on the licensed spectrum. However, LTE/LTE-A networks withunlicensed spectrum deployed on a given channel by multiple SPs may beconfigured to be synchronous across the multiple SPs. One approach toincorporate both the above features may involve using a constant timingoffset between LTE/LTE-A with and without unlicensed spectrum for agiven SP. An LTE/LTE-A network with unlicensed spectrum may provideunicast and/or multicast services according to the needs of the SP.Moreover, LTE/LTE-A network with unlicensed spectrum may operate in abootstrapped mode in which LTE cells act as anchor and provide relevantunlicensed band cell information (e.g., radio frame timing, commonchannel configuration, system frame number or SFN, etc.). In this mode,there may be close interworking between LTE/LTE-A with and withoutunlicensed spectrum. For example, the bootstrapped mode may support thesupplemental downlink and the carrier aggregation modes described above.The PHY-MAC layers of the LTE/LTE-A network with unlicensed spectrum mayoperate in a standalone mode in which the LTE/LTE-A network withunlicensed spectrum operates independently from an LTE network. In thiscase, there may be a loose interworking between LTE/LTE-A with andwithout unlicensed spectrum on RLC-level aggregation with co-locatedlicensed and unlicensed band cells, or multiflow across multiple cellsand/or base stations, for example.

The techniques described herein are not limited to LTE, and may also beused for various wireless communications systems such as CDMA, TDMA,FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and“network” are often used interchangeably. A CDMA system may implement aradio technology such as CDMA2000, Universal Terrestrial Radio Access(UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards.IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1×, 1×,etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, HighRate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) andother variants of CDMA. A TDMA system may implement a radio technologysuch as Global System for Mobile Communications (GSM). An OFDMA systemmay implement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunication System (UMTS). LTE and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description below, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

Thus, the following description provides examples, and is not limitingof the scope, applicability, or configuration set forth in the claims.Changes may be made in the function and arrangement of elementsdiscussed without departing from the spirit and scope of the disclosure.Various embodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods described may beperformed in an order different from that described, and various stepsmay be added, omitted, or combined. Also, features described withrespect to certain embodiments may be combined in other embodiments.

Referring first to FIG. 1, a diagram illustrates an example of awireless communications system or network 100. The system 100 includesbase stations (or cells) 105, communication devices 115, and a corenetwork 130. The base stations 105 may communicate with thecommunication devices 115 under the control of a base station controller(not shown), which may be part of the core network 130 or the basestations 105 in various embodiments. Base stations 105 may communicatecontrol information and/or user data with the core network 130 throughbackhaul links 132. In embodiments, the base stations 105 maycommunicate, either directly or indirectly, with each other overbackhaul links 134, which may be wired or wireless communication links.The system 100 may support operation on multiple carriers (waveformsignals of different frequencies). Multi-carrier transmitters cantransmit modulated signals simultaneously on the multiple carriers. Forexample, each communication link 125 may be a multi-carrier signalmodulated according to the various radio technologies described above.Each modulated signal may be sent on a different carrier and may carrycontrol information (e.g., reference signals, control channels, etc.),overhead information, data, etc.

The base stations 105 may wirelessly communicate with the devices 115via one or more base station antennas. Each of the base station 105sites may provide communication coverage for a respective geographicarea 110. In some embodiments, base stations 105 may be referred to as abase transceiver station, a radio base station, an access point, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, eNodeB (eNB), Home NodeB, a Home eNodeB, or some other suitableterminology. The coverage area 110 for a base station may be dividedinto sectors making up only a portion of the coverage area (not shown).The system 100 may include base stations 105 of different types (e.g.,macro, micro, and/or pico base stations). There may be overlappingcoverage areas for different technologies.

In some embodiments, the system 100 is an LTE/LTE-A network thatsupports one or more communication modes of operation or deploymentscenarios using unlicensed spectrum. In other embodiments, the system100 may support wireless communications using an unlicensed spectrum andan access technology different from LTE/LTE-A with unlicensed spectrum,or a licensed spectrum and an access technology different fromLTE/LTE-A. The terms evolved Node B (eNB) and user equipment (UE) may begenerally used to describe the base stations 105 and devices 115,respectively. The system 100 may be a Heterogeneous LTE/LTE-A networkwith or without unlicensed spectrum in which different types of eNBsprovide coverage for various geographical regions. For example, each eNB105 may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. Small cells such as pico cells,femto cells, and/or other types of cells may include low power nodes orLPNs. A macro cell generally covers a relatively large geographic area(e.g., several kilometers in radius) and may allow unrestricted accessby UEs with service subscriptions with the network provider. A pico cellwould generally cover a relatively smaller geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell would also generally cover a relatively smallgeographic area (e.g., a home) and, in addition to unrestricted access,may also provide restricted access by UEs having an association with thefemto cell (e.g., UEs in a closed subscriber group (CSG), UEs for usersin the home, and the like). An eNB for a macro cell may be referred toas a macro eNB. An eNB for a pico cell may be referred to as a pico eNB.And, an eNB for a femto cell may be referred to as a femto eNB or a homeeNB. An eNB may support one or multiple (e.g., two, three, four, and thelike) cells.

The core network 130 may communicate with the eNBs 105 via a backhaul132 (e.g., S1, etc.). The eNBs 105 may also communicate with oneanother, e.g., directly or indirectly via backhaul links 134 (e.g., X2,etc.) and/or via backhaul links 132 (e.g., through core network 130).The system 100 may support synchronous or asynchronous operation. Forsynchronous operation, the eNBs may have similar frame and/or gatingtiming, and transmissions from different eNBs may be approximatelyaligned in time. For asynchronous operation, the eNBs may have differentframe and/or gating timing, and transmissions from different eNBs maynot be aligned in time. The techniques described herein may be used foreither synchronous or asynchronous operations.

The UEs 115 are dispersed throughout the system 100, and each UE may bestationary or mobile. A UE 115 may also be referred to by those skilledin the art as a mobile station, a subscriber station, a mobile unit, asubscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology. A UE 115 may be acellular phone, a personal digital assistant (PDA), a wireless modem, awireless communication device, a handheld device, a tablet computer, alaptop computer, a cordless phone, a wireless local loop (WLL) station,or the like. A UE may be able to communicate with macro eNBs, pico eNBs,femto eNBs, relays, and the like.

The communications links 125 shown in system 100 may include uplink (UL)transmissions from a mobile device 115 to a base station 105, and/ordownlink (DL) transmissions, from a base station 105 to a mobile device115. The downlink transmissions may also be called forward linktransmissions while the uplink transmissions may also be called reverselink transmissions. The downlink transmissions may be made using alicensed spectrum, an unlicensed spectrum, or both. Similarly, theuplink transmissions may be made using a licensed spectrum, anunlicensed spectrum, or both.

In some embodiments of the system 100, various deployment scenarios forLTE/LTE-A with unlicensed spectrum may be supported including asupplemental downlink (SDL) mode in which LTE downlink capacity in alicensed spectrum may be offloaded to an unlicensed spectrum, a carrieraggregation mode in which both LTE downlink and uplink capacity may beoffloaded from a licensed spectrum to an unlicensed spectrum, and astandalone mode in which LTE downlink and uplink communications betweena base station (e.g., eNB) and a UE may take place in an unlicensedspectrum. Base stations 105 as well as UEs 115 may support one or moreof these or similar modes of operation. OFDMA communications signals maybe used in the communications links 125 for LTE downlink transmissionsin an unlicensed spectrum, while SC-FDMA communications signals may beused in the communications links 125 for LTE uplink transmissions in anunlicensed spectrum. Additional details regarding the implementation ofLTE/LTE-A deployment scenarios or modes of operation with unlicensedspectrum in a system such as the system 100, as well as other featuresand functions related to the operation of LTE/LTE-A with unlicensedspectrum, are provided below with reference to FIGS. 2A-14B.

Turning next to FIG. 2A, a diagram 200 shows examples of a supplementaldownlink mode and of a carrier aggregation mode for an LTE/LTE-A networkthat supports communications using unlicensed spectrum. The diagram 200may be an example of portions of the system 100 of FIG. 1. Moreover, thebase station 105-a may be an example of the base stations 105 of FIG. 1,while the UEs 115-a may be examples of the UEs 115 of FIG. 1.

In the example of a supplemental downlink mode in diagram 200, the basestation 105-a may transmit OFDMA communications signals to a UE 115-ausing a downlink 205. The downlink 205 is associated with a frequency F1in an unlicensed spectrum. The base station 105-a may transmit OFDMAcommunications signals to the same UE 115-a using a bidirectional link210 and may receive SC-FDMA communications signals from that UE 115-ausing the bidirectional link 210. The bidirectional link 210 isassociated with a frequency F4 in a licensed spectrum. The downlink 205in the unlicensed spectrum and the bidirectional link 210 in thelicensed spectrum may operate concurrently. The downlink 205 may providea downlink capacity offload for the base station 105-a. In someembodiments, the downlink 205 may be used for unicast services (e.g.,addressed to one UE) services or for multicast services (e.g., addressedto several UEs). This scenario may occur with any service provider(e.g., traditional mobile network operator or MNO) that uses a licensedspectrum and needs to relieve some of the traffic and/or signalingcongestion.

In one example of a carrier aggregation mode in diagram 200, the basestation 105-a may transmit OFDMA communications signals to a UE 115-ausing a bidirectional link 215 and may receive SC-FDMA communicationssignals from the same UE 115-a using the bidirectional link 215. Thebidirectional link 215 is associated with the frequency F1 in theunlicensed spectrum. The base station 105-a may also transmit OFDMAcommunications signals to the same UE 115-a using a bidirectional link220 and may receive SC-FDMA communications signals from the same UE115-a using the bidirectional link 220. The bidirectional link 220 isassociated with a frequency F2 in a licensed spectrum. The bidirectionallink 215 may provide a downlink and uplink capacity offload for the basestation 105-a. Like the supplemental downlink described above, thisscenario may occur with any service provider (e.g., MNO) that uses alicensed spectrum and needs to relieve some of the traffic and/orsignaling congestion.

In another example of a carrier aggregation mode in diagram 200, thebase station 105-a may transmit OFDMA communications signals to a UE115-a using a bidirectional link 225 and may receive SC-FDMAcommunications signals from the same UE 115-a using the bidirectionallink 225. The bidirectional link 225 is associated with the frequency F3in an unlicensed spectrum. The base station 105-a may also transmitOFDMA communications signals to the same UE 115-a using a bidirectionallink 230 and may receive SC-FDMA communications signals from the same UE115-a using the bidirectional link 230. The bidirectional link 230 isassociated with the frequency F2 in the licensed spectrum. Thebidirectional link 225 may provide a downlink and uplink capacityoffload for the base station 105-a. This example and those providedabove are presented for illustrative purposes and there may be othersimilar modes of operation or deployment scenarios that combineLTE/LTE-A with and without unlicensed spectrum for capacity offload.

As described above, the typical service provider that may benefit fromthe capacity offload offered by using LTE/LTE-A with unlicensed spectrumis a traditional MNO with LTE spectrum. For these service providers, anoperational configuration may include a bootstrapped mode (e.g.,supplemental downlink, carrier aggregation) that uses the LTE primarycomponent carrier (PCC) on the licensed spectrum and the secondarycomponent carrier (SCC) on the unlicensed spectrum.

In the supplemental downlink mode, control for LTE/LTE-A with unlicensedspectrum may be transported over the LTE uplink (e.g., uplink portion ofthe bidirectional link 210). One of the reasons to provide downlinkcapacity offload is because data demand is largely driven by downlinkconsumption. Moreover, in this mode, there may not be a regulatoryimpact since the UE is not transmitting in the unlicensed spectrum.There is no need to implement listen-before-talk (LBT) or carrier sensemultiple access (CSMA) requirements on the UE. However, LBT may beimplemented on the base station (e.g., eNB) by, for example, using aperiodic (e.g., every 10 milliseconds) clear channel assessment (CCA)and/or a grab-and-relinquish mechanism aligned to a radio frameboundary.

In the carrier aggregation mode, data and control may be communicated inLTE (e.g., bidirectional links 210, 220, and 230) while data may becommunicated in LTE/LTE-A with unlicensed spectrum (e.g., bidirectionallinks 215 and 225). The carrier aggregation mechanisms supported whenusing LTE/LTE-A with unlicensed spectrum may fall under a hybridfrequency division duplexing-time division duplexing (FDD-TDD) carrieraggregation or a TDD-TDD carrier aggregation with different symmetryacross component carriers.

FIG. 2B shows a diagram 200-a that illustrates an example of astandalone mode for LTE/LTE-A with unlicensed spectrum. The diagram200-a may be an example of portions of the system 100 of FIG. 1.Moreover, the base station 105-b may be an example of the base stations105 of FIG. 1 and the base station 105-a of FIG. 2A, while the UE 115-bmay be an example of the UEs 115 of FIG. 1 and the UEs 115-a of FIG. 2A.

In the example of a standalone mode in diagram 200-a, the base station105-b may transmit OFDMA communications signals to the UE 115-b using abidirectional link 240 and may receive SC-FDMA communications signalsfrom the UE 115-b using the bidirectional link 240. The bidirectionallink 240 is associated with the frequency F3 in an unlicensed spectrumdescribed above with reference to FIG. 2A. The standalone mode may beused in non-traditional wireless access scenarios, such as in-stadiumaccess (e.g., unicast, multicast). The typical service provider for thismode of operation may be a stadium owner, cable company, event hosts,hotels, enterprises, and large corporations that do not have licensedspectrum. For these service providers, an operational configuration forthe standalone mode may use the PCC on the unlicensed spectrum.Moreover, LBT may be implemented on both the base station and the UE.

Turning next to FIG. 3, a diagram 300 illustrates an example of carrieraggregation when using LTE concurrently in licensed and unlicensedspectrum according to various embodiments. The carrier aggregationscheme in diagram 300 may correspond to the hybrid FDD-TDD carrieraggregation described above with reference to FIG. 2A. This type ofcarrier aggregation may be used in at least portions of the system 100of FIG. 1. Moreover, this type of carrier aggregation may be used in thebase stations 105 and 105-a of FIG. 1 and FIG. 2A, respectively, and/orin the UEs 115 and 115-a of FIG. 1 and FIG. 2A, respectively.

In this example, an FDD (FDD-LTE) may be performed in connection withLTE in the downlink, a first TDD (TDD1) may be performed in connectionwith LTE/LTE-A with unlicensed spectrum, a second TDD (TDD2) may beperformed in connection with LTE, and another FDD (FDD-LTE) may beperformed in connection with LTE in the uplink. TDD1 results in a DL:ULratio of 6:4, while the ratio for TDD2 is 7:3. On the time scale, thedifferent effective DL:UL ratios are 3:1, 1:3, 2:2, 3:1, 2:2, and 3:1.This example is presented for illustrative purposes and there may beother carrier aggregation schemes that combine the operations ofLTE/LTE-A with and without unlicensed spectrum.

FIG. 4 shows a block diagram of a design of a base station/eNB 105 and aUE 115, which may be one of the base stations/eNBs and one of the UEs inFIG. 1. The eNB 105 may be equipped with antennas 434 a through 434 t,and the UE 115 may be equipped with antennas 452 a through 452 r. At theeNB 105, a transmit processor 420 may receive data from a data source412 and control information from a controller/processor 440. The controlinformation may be for the physical broadcast channel (PBCH), physicalcontrol format indicator channel (PCFICH), physical hybrid automaticrepeat request indicator channel (PHICH), physical downlink controlchannel (PDCCH), etc. The data may be for the physical downlink sharedchannel (PDSCH), etc. The transmit processor 420 may process (e.g.,encode and symbol map) the data and control information to obtain datasymbols and control symbols, respectively. The transmit processor 420may also generate reference symbols, e.g., for the primarysynchronization signal (PSS), secondary synchronization signal (SSS),and cell-specific reference signal. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 430 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols, if applicable, and may provide output symbol streamsto the modulators (MODS) 432 a through 432 t. Each modulator 432 mayprocess a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 432 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. Downlink signals frommodulators 432 a through 432 t may be transmitted via the antennas 434 athrough 434 t, respectively.

At the UE 115, the antennas 452 a through 452 r may receive the downlinksignals from the eNB 105 and may provide received signals to thedemodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 115 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 115, a transmit processor 464 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 462 and control information (e.g., for the physical uplinkcontrol channel (PUCCH)) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the eNB 105. At the eNB 105, the uplink signals from theUE 115 may be received by the antennas 434, processed by the modulators432, detected by a MIMO detector 436 if applicable, and furtherprocessed by a receive processor 438 to obtain decoded data and controlinformation sent by the UE 115. The processor 438 may provide thedecoded data to a data sink 439 and the decoded control information tothe controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at theeNB 105 and the UE 115, respectively. The controller/processor 440and/or other processors and modules at the eNB 105 may perform or directthe execution of various processes for the techniques described herein.The controllers/processor 480 and/or other processors and modules at theUE 115 may also perform or direct the execution of the functional blocksillustrated in FIGS. 8A-8B and 13A-13B, and/or other processes for thetechniques described herein. The memories 442 and 482 may store data andprogram codes for the eNB 105 and the UE 115, respectively. A scheduler444 may schedule UEs for data transmission on the downlink and/oruplink.

With the implementation of wireless technologies for communication usingLTE/LTE-A with unlicensed spectrum, various adaptations may be desirablein order to accommodate LTE operations over an unlicensed band withefficiency and a little change from the current LTE standards aspossible. For example, various uplink procedures may be adapted for LTEoperations with unlicensed spectrum in LTE/LTE-A deployments withunlicensed spectrum.

Similar to the downlink structure in LTE/LTE-A operations withunlicensed spectrum, there are a certain number of transmissionopportunities not subject to clear channel assessment (CCA)requirements. Thus, there may be a certain number of transmissionopportunities that may also be autonomous or guaranteed (not subject toCCA) in uplink communication. For purposes of this disclosure autonomoustransmissions and guaranteed transmissions may be used interchangeablyto mean the same guaranteed transmission opportunity. This guaranteedtransmission opportunity may be beneficial for transmitting uplinksignals/channels in a guaranteed manner. For example, uplinkcommunications that may be important for guaranteed transmissioninclude: sounding reference signals (SRS), which are used in powercontrol and uplink/downlink scheduling, scheduling request (SR), channelstate information (CSI) feedback, uplink discovery signals for peer topeer communications, physical random access channel (PRACH), physicaluplink shared channel (PUSCH) (e.g., initial PUSCH transmission as partof RACH procedures). This guaranteed transmission opportunity may beapplicable to standalone LTE/LTE-A deployments with unlicensed spectrum,as well as potentially to carrier aggregation (CA) deployments.

In addition to the guaranteed transmission of uplink signals, LTE/LTE-Awith unlicensed spectrum may also provide additional opportunistictransmission of uplink signals as well. The additional uplink signalsthat may be opportunistically transmitted in CCA-based subframes mayprovide additional signal instances that may be received at theassociated base stations more frequently than the fixed period. In suchCCA-based subframes, if the UE detects a clear CCA, then it may transmituplink signals at some point before the expiration of the clear period.After detecting a clear CCA, the transmission stream are guaranteed tobe available for a predetermined duration, such as 5-10 ms. Thus, theassociated base stations may receive certain uplink signals morefrequently. However, inter-frequency status should be based on theguaranteed transmission subframes.

Various aspects of the present disclosure provide for differentinteractions between the downlink autonomous transmissions and theuplink autonomous transmissions. In some aspects of the disclosure, theuplink and downlink autonomous transmissions may be separately managed.Accordingly, each may have different periodicities and/or differentsubframe offsets. In alternative aspects of the present disclosure, theuplink and downlink autonomous transmissions may be jointly managed. Inparticular, uplink autonomous transmissions may operate in a slaveconfiguration to the downlink autonomous transmissions. The jointmanagement may, thus, include the same periodicity and/or correlatedsubframe offsets. Aspects that jointly manage the autonomoustransmissions may offer more efficient operations as linking thedownlink and uplink operations typically results in improved systemperformance.

LTE/LTE-A deployments with unlicensed spectrum that use WIFI nodesoperate under a 5% flexible transmission budget. The 5% flexibletransmission budget prevents a WIFI node from autonomously transmittingmore than 5% within any 50 ms period. Accordingly, one aspect of thepresent disclosure suggests a fixed periodicity of 80 ms for guaranteedtransmissions. However, the 5% flexible transmission budget requirementsare measured over a 50 ms period. Thus, the fixed period for guaranteedtransmissions may also be set to 50 ms. While 80 ms offers the benefitof being more evenly divisible or comparable to many different systemparameters, a shorter period, such as 50 ms would provide moreopportunities for guaranteed operations. Other times may be consideredas well, e.g., 60 ms, 70 ms, and the like.

FIG. 5 is a block diagram illustrating a transmission timeline 50 for anLTE/LTE-A deployment with unlicensed spectrum configured according toone aspect of the present disclosure. Transmission timeline 50illustrates the downlink guaranteed transmissions for LTE/LTE-A withunlicensed spectrum (LTE-US) eNB 500 and the uplink guaranteedtransmission for LTE-US UE1 501 which are jointly managed. The uplinkguaranteed transmissions from LTE-US UE2 502 and LTE-US U3 503 aretransmitted according to different periodicities and offsets than thetransmissions from LTE-US UE1 501. The different periodicities andoffsets may be due to different discontinuous reception (DRX)operations, due to load balancing/interference coordination, or thelike. In the joint management scenario of FIG. 5, the uplink guaranteedtransmissions of LTE-US UE1 501 are slaved to the downlink guaranteedtransmissions of LTE-US eNB 500.

As illustrated in FIG. 5, LTE-US eNB 500 sends its downlink guaranteedtransmission and LTE-US UE1 501 sends its corresponding uplinkguaranteed transmission a time, T1, after the downlink transmission.Each of LTE-US eNB 500 and LTE-US UE1 501 transmit their respectiveguaranteed transmissions at the same fixed period, such as, for example,50 ms, 60 ms, 80 ms, or the like. In consideration of the triggeringtime, T1, after which LTE-US UE1 501 sends its uplink guaranteedtransmission, it may be beneficial to have T1<T2, to facilitate fastrandom access procedure. The processing time of LTE-US UE1 501 allowsLTE-US UE1 501 to receive the downlink guaranteed transmission fromLTE-US eNB 500 at 504 and send uplink guaranteed transmissions at 506.Over time T2, LTE-US eNB 500 may process SR, CSI feedback, and the like,received at 506, and send downlink guaranteed transmission 505. LTE-USUE 501 may then transmit uplink guaranteed transmission 507 triggeredagain by the receipt of downlink guaranteed transmission 505.

It should be noted that the duration of each guaranteed transmissioninstance in the uplink may be the same or different than that of thedownlink guaranteed transmission. For example, the downlink guaranteedtransmission occupies 4 symbols over 2 subframes. Thus, in variousaspects of the disclosure, the uplink guaranteed transmission may alsooccupy 4 symbols over 2 subframes. Note that in LTE/LTE-A withunlicensed spectrum, the uplink transmissions may be single carrierfrequency division multiple access (SC-FDMA) signals, signals based onmulti-cluster resource allocation where each cluster is contiguousresource allocation, signals based on interleaved resource allocation,signals based on OFDM, etc. However, in order to maximize reuse ofexisting LTE uplink design, a transmission duration of 7 symbols over 1slot may be a more natural duration than the 4 symbols duration. Thus,in certain aspects of the disclosure, uplink guaranteed transmissionsmay have a duration of 4 symbols over 2 subframes, while other aspectsmay use other durations, such as 7 symbols over 1 slot. Other durationsare possible as well, e.g., 6 symbols.

FIG. 6 is a block diagram illustrating a transmission timeline 60 in anLTE/LTE-A deployment with unlicensed spectrum configured according toone aspect of the present disclosure. Four transmissions from LTE-US UE1600-LTE-US UE4 603 represent uplink guaranteed transmissions at fixedintervals. LTE-US UE1 600 and LTE-US UE2 602 transmit their respectiveguaranteed transmissions at the same time and interval. In order toincrease frequency reuse for guaranteed transmissions, the guaranteedtransmissions of LTE-US UE1 600 and LTE-US UE2 602 are frequencydivision multiplexed (FDM) into FDM transmission 604. The guaranteedtransmissions from LTE-US UE3 602 and LTE-US UE4 603 are alsotransmitted at the same time and interval, and may also be FDM intoanother FDM transmission. Further increasing the reuse of the guaranteedtransmissions, the FDM transmission 604 and the FDM transmission ofLTE-US UE3 602 and LTE-US UE4 603 may then each be time divisionmultiplexed (TDM) 605. Thus, the reuse may facilitate co-existence ofdifferent deployments (e.g., from different operators).

It should be noted that the various reuse scenarios may be realized viaTDM within a subframe (different symbols in a subframe, or differentslots in a subframe), TDM across subframes (different subframes fordifferent deployments), FDM within a symbol, or a combination thereof.

One of the uplink signals that may be sent by UEs using the guaranteedtransmission subframes identified in LTE/LTE-A deployments withunlicensed spectrum are PRACH/RACH signals. Random access proceduresallow for the UE to connect to a new cell whether connecting initiallyon startup or connecting on handover. When transmitting PRACH usingLTE/LTE-A guaranteed transmissions with unlicensed spectrum, the RACHresources may be managed through various levels of multiplexing. FIG. 7is a block diagram illustrating a system bandwidth 70 of an LTE/LTE-Adeployment with unlicensed spectrum configured according to one aspectof the present disclosure. As illustrated, system bandwidth 70 isdivided into 100 physical resource blocks. The multiplexing of PRACH maybe based on frequency division multiplexing (FDM) and/or code divisionmultiplexing (CDM). For example, as illustrated in FIG. 7, the entire100 PRBs are be grouped into 10 groups, of 10 PRBs each. Each group maybe interleaved in frequency to span at least 80% of system bandwidth 70.For example, PRACH Group 1 occupies every tenth PRB, e.g., PRBs 1, 11,21, . . . , and 91. In selected aspects of the present disclosure, eachPRACH is assigned to only one PRACH group. In additional aspects of thepresent disclosure, PRACH for different UEs may be multiplexed using CDMwithin a single group. For example, the PRACH Group 1 instances areillustrated, in the alternative, with PRACH from both UE1 and UE2. ThePRACH signaling from UE1 and UE2 are combined through CDM in a singlePRACH group.

It should be noted that, while illustrated in the alternative withmultiple PRACH groups multiplexed using both FDM and CDM over systembandwidth 70, additional aspects of the preset disclosure may only useCDM for combining PRACH from UEs in the same frequency. The variousaspects of the present disclosure are not limited to any specific reusescheme.

In LTE communications, random access procedures are performed on a percarrier basis. However, in various aspects of the present disclosure, itmay be possible to enable a cross-carrier random access procedure, forexample, in an LTE/LTE-A cell with unlicensed spectrum equipped withmultiple carriers and UEs capable to wideband RF. FIGS. 8A and 8B arefunctional block diagrams illustrating example blocks executed toimplement one aspect of the present disclosure. At block 800, anLTE/LTE-A UE with unlicensed spectrum generates a random access requestfor connecting to a cell. At block 801, the UE transmits the randomaccess request to a base station over a first carrier of a plurality ofcarriers operated in a cell serviced by the serving base station. Atblock 803, an LTE/LTE-A base station with unlicensed spectrum receivesthe random access request from the UE over the first carrier of aplurality of carriers available in the cell. At block 802, the UEmonitors the plurality of carriers for a random access response toconnect to the cell. At block 804, the LTE/LTE-A base station withunlicensed spectrum generates a random access response, in response tothe random access request. At block 805, the LTE/LTE-A base station withunlicensed spectrum directs transmission of the random access responseto the UE over another carrier of the plurality of carriers. Thus, insuch cross-carrier random access procedures, PRACH may be initiated on afirst carrier, while the UE monitors a different carrier, either alongwith or instead of the first carrier, for any random access response.

In LTE/LTE-A deployments with unlicensed spectrum, the random accessprocedure may be supported in both guaranteed (non-CCA) andnon-guaranteed (CCA) uplink and/or downlink subframes. FIG. 9 is a blockdiagram illustrating a transmission timeline 90 in an LTE/LTE-Acommunication system with unlicensed spectrum configured according toone aspect of the present disclosure. Timeline 90 illustrates downlinktransmission opportunities from LTE-US eNB 900 and uplink transmissionopportunities from LTE-US UE 901. LTE-US UE 901 may transmit uplink RACHeither through guaranteed RACH transmission opportunities at non-CCAsubframes 911 and 916 or non-guaranteed RACH transmission opportunitiesat CCA subframes 910, 912-915, and 917 after receiving a CCA clearsignal. LTE-US eNB 900 may send random access response (RAR) messagesalso either through guaranteed RAR transmission opportunities at non-CCAsubframes 902 and 907 or non-guaranteed RAR transmission opportunitiesat CCA subframes 903-906, 908, and 909 after receiving a CCA clearsignal. Guaranteed transmission opportunities of RACH and RAR messagesoccur at the fixed period associated with guaranteed transmissions(e.g., 50 ms, 60 ms, 80 ms, etc.). The set of subframes for RACHopportunities can be maintained by an eNB.

It should be noted that in various aspects of the present disclosure,only one PRACH format is sufficient. Due to reduced coverage range forLTE/LTE-A nodes with unlicensed spectrum, PRACH may occupy a fraction ofa subframe. For example, the PRACH request may only be provided in oneslot or one or more symbols (similar to PRACH format 4). The actualchannel can be similar to PUSCH (or PUCCH) for the case of simplifiedRACH procedure, since it contains some payload.

In typical RACH procedures a UE transmits the random access request andthen waits for a certain response window before a RACH re-transmissionis triggered. Each successive re-transmission is also ramped up withpower. The reasoning for the re-transmission/power ramp-up process is toconserve power, by not transmitting RACH at its maximum power, andgradually increasing the power of the re-transmissions in case thetargeted base station simply cannot reliably receive and interpret therandom access request. This RACH re-transmission process may involvemultiple transmissions until the UE receives the corresponding randomaccess response, and these multiple transmissions may have powerramp-ups with a step size (including 0 dB or no power ramp-ups)configurable by an LTE/LTE-A base station with unlicensed spectrum.However, in order to determine whether to perform a re-transmission ofPRACH in an LTE/LTE-A deployment with unlicensed spectrum, the UE shouldbe capable of distinguishing the following two transmissions states of acell: State 1 is an incapable transmission state in which the cell doesnot have a chance to transmit the response within a given responsewindow. In the incapable transmission state, the base station has nothad an opportunity within the response window to transmit a randomaccess response because there either has been no guaranteed transmissionsubframes (non-CCA subframes) or the base station has not been able todetect a clearance during a CCA, non-guaranteed subframe. State 2 is acapable state in which the cell has had chance to transmit the responsewithin the given response window, either because it has had a guaranteedsubframe or has detected clearance on a CCA subframe, but the UE hasstill not received the response. With State 2, the UE may not receivethe response because of various reasons, such as the eNB failing toreceive the request message, or even the UE failing to receive theresponse from the base station, etc.

The UE should be able to detect these two states and take differentactions accordingly. The detection may be based on detection of channelusage pilot signals (CUPS), sometimes referred to as channel usagebeacon signals (CUBS), cell-specific reference signals (CRS), channelstate information reference signals (CSI-RS), etc. If the UE detects oneof these reference signals, that means that the base station has beenable to make transmissions, which means that it has either had aguaranteed subframe or a CCA-cleared subframe. The UE would, thereforedetermine that the base station is in State 2, the capable transmissionstate, and would trigger re-transmission after the response window hasexpired without receiving a random access response. However, if the UEfails to detect any reference signal transmissions from the basestation, that may mean that the base station has not encountered eithera guaranteed subframe or a CCA-cleared subframe. In this situation, theUE would determine that the base station is in State 1, the incapabletransmission state. In State 1, the UE should not attemptre-transmissions and should extending the response window for the basestation to be able to respond. If the extended response window againpasses with the UE having received the response, then the UE may attemptre-transmissions.

With reference to FIG. 9, LTE-US UE 901 transmits an initial randomaccess request at guaranteed subframe 911 and begins to monitor for arandom access response from LTE-US eNB 900. The first RAR transmissionopportunity arises at non-guaranteed subframe 903. However, at subframe903, LTE-US eNB 900 does not detect a CCA-clear. Therefore, LTE-US eNB900 is incapable of any transmissions. LTE-US UE 901 w continues tomonitor during the response window for the random access response. Ateach of non-guaranteed subframes 904 and 905, LTE-US eNB 900 fails todetect a CCA-clear. As such, LTE-US UE 901 does not receive a randomaccess response message. The response window ends for LTE-US UE 901 atthe time associated with non-guaranteed subframe 905. However, LTE-US UE901 has not detected any reference signals from LTE-US eNB 900 sincetransmitting the initial random access request at subframe 911. LTE-USUE 901, therefore, determines that LTE-US eNB 900 is in an incapabletransmission state and, accordingly, extends the response window andassociate re-transmission time gap. At guaranteed subframe 907, LTE-USeNB 900 still does not send a random access response message to LTE-USUE 901. With the occurrence of the guaranteed subframe 907, UE 901 nowdetermines that LTE-US eNB 900 is in a capable transmission state, butbecause it still has not received a random access response from LTE-USeNB 900, LTE-US UE 901 triggers a re-transmission and ramp-up oftransmission power at guaranteed subframe 916. As such, the PRACHre-transmission process is updated for the LTE/LTE-A deployment withunlicensed spectrum to save unnecessary re-transmission and ramp-up ofPRACH transmission power.

As noted, LTE/LTE-A UEs with unlicensed spectrum can look for the randomaccess response in both guaranteed and non-guaranteed subframes. Theresponse window can take into account the differences among threedifferent subframe types at the LTE/LTE-A base station with unlicensedspectrum: guaranteed subframes; CCA-cleared non-guaranteed subframes;and CCA-not-cleared non-guaranteed subframes. As an example, the UE maymonitor the response starting from N-ms after PRACH transmission andkeep monitoring until the end of a guaranteed subframe, oralternatively, either a CCA-cleared non-guaranteed subframe or aguaranteed subframe.

It should be noted that CUPS/CUBs may be used for both channelsynchronization and channel reservation. After determining thatunlicensed spectrum is available (e.g., by performing a successful CCA),a base station may fill each of the CCA slots following its performanceof a successful CCA with CUPS/CUBs. The CUPS/CUBS may include one ormore signals that are detectable by other devices to let the otherdevices know the unlicensed spectrum (or at least a channel thereof) hasbeen reserved for use by another device. CUPS/CUBs may be detected byboth LTE and WiFi devices. Unlike most LTE signals, however, which beginat a subframe boundary, CUPS/CUBS may begin at an OFDM symbol boundary.That is, a device that performs a CCA for the channel after anotherdevice begins to transmit CUPS/CUBS on the channel may detect the energyof the CUPS/CUBS and determine that the channel is currentlyunavailable.

Considering the non-guaranteed subframes and length of time betweenguaranteed subframes, aspects of the present disclosure set the responsewindow or time gap between re-transmissions to take into account theextended response window. For example, one possibility is to determinethe time gap based on first subframe (or frame) that the base stationhas a chance to respond, either due to encountering a guaranteedsubframe or CCA cleared non-guaranteed subframe.

For guaranteed transmissions of uplink signals no CCA investigation isnecessary. However, if a UE has been idle for a long time (e.g., for twoor more consecutive frames), then the UE may immediately send PRACH orother uplink transmissions without violating the 5% duty cycle flexibletransmission rule over the predetermined 50 ms. With this scenario, eventhough the UE may be sending uplink transmissions over a CCA subframe,because of the substantial idle time the uplink transmission will likelynot violate the CCA protections.

FIG. 10 is a block diagram illustrating a transmission timeline 1000 ofan LTE-US UE 1001 configured according to one aspect of the presentdisclosure. LTE-US 1001 has been in an idle mode for at least 50 msbefore the first illustrated guaranteed transmission opportunity atnon-CCA subframe 1002. Because LTE-US UE 1001 has been in an idle modefor this period of time, when LTE-US UE 1001 desires to connect to thecell after non-CCA subframe 1002, it may immediately transmit the randomaccess request at the next available transmission opportunity, which isCCA subframe 1003. While LTE-US UE 1001 would normally be required tofirst receive a CCA clear before transmitting uplink signals on CCAsubframe 1003, because of the substantial idle period, LTE-US UE 1001 isable to transmit the random access request on CCA subframe 1003 withoutfirst obtaining the CCA clear. However, the offset for guaranteedinitial access may not be aligned with the offset for guaranteedtransmission for regular operations. If so, then LTE-US UE 1001 may needto make adjustments to the guaranteed transmissions in order to adjustto the normal offset. For a subsequent transmission opportunity, LTE-USUE 1001 would not be able to transmit again within 50 ms of the initialrandom access transmission.

The next guaranteed transmission subframe after CCA subframe 1003 isnon-CCA subframe 1004. However, non-CCA subframe 1004 is within 50 msfrom CCA subframe 1003. If LTE-US UE 1001 were to transmit additionaluplink signals or random access re-transmissions at non-CCA subframe1004, it may then violate the 5% duty cycle flexible transmission limitwithin the 50 ms period. In such a circumstance, LTE-US UE 1001 may skiptransmission on the guaranteed subframe completely. It should be noted,however, that LTE-US UE 1001 may perform a CCA request to determinewhether or not such transmissions would, in fact, violate the 5% limit.If LTE-US UE 1001 were to receive a CCA clear, then it could thentransmit the additional uplink signals or re-transmitted random accessrequests. The next guaranteed transmission opportunity for LTE-US UE1001 fall at non-CCA subframe 1005. Non-CCA subframe 1005 lies outsideof the 50 ms window from CCA subframe 1003, but also does not match theoffset that starts from CCA subframe 1003. Accordingly, LTE-US UE 1001may adjust the offset for guaranteed transmission for regularoperations, in order to begin guaranteed transmissions at non-CCAsubframe 1005.

In the current random access procedure, 4-messages exchange between theUE and base station. The first message, Msg 1, includes the PRACH by UE;the second message, Msg 2, includes the RAR response by the basestation; the third message, Msg 3, includes the initial PUSCHtransmission, which may contain a radio resource control (RRC)connection request from the UE; and the fourth message, Msg 4, includesconnection setup information from the base station, which may containRRC connection setup and the like. In some situations, such as duringhandover, the fourth message, Msg 4, would not be necessary.

Various aspects of the present disclosure provide for a simplified RACHprocedure. For example, various aspects simplify the RACH procedure to 2or 3 messages. FIG. 11A is a call flow diagram 1100 illustrating a callflow in an LTE/LTE-A communication system with unlicensed spectrumbetween an eNB 1101 and UE 1102 configured according to one aspect ofthe present disclosure. At time 1103, UE 1102 sends a combined randomaccess request message that includes the random access request andinitial PUSCH transmission. At time 1104, eNB 1101, having received therandom access request with the initial PUSCH information, responds witha combined random access response message that includes the randomaccess response to UE 1102 and additional connection setup information,such as the RRC connection setup message.

In various embodiments of the disclosure the 2-step simplified RACHprocedure provides a much more efficient process. However, there may beoccasions where the latency between Msg 3, which was included by UE 1102in the combined random access request message, and Msg 4, which wasincluded by eNB 1101 in the combined random access response message. Theinitial PUSCH waits for acknowledgment that comes with the Msg 4connection setup information. Thus, while waiting for thisconfirmation/acknowledgement, UE 1102 may continue monitoring theresponse window for re-transmission and power ramp-ups of the RACHrequests. Accordingly, alternative aspects of the present disclosureprovide for a 3-step simplified RACH procedure. FIG. 11B is a call flowdiagram 1105 illustrating a call flow in an LTE/LTE-A communicationsystem with unlicensed spectrum between the eNB 1101 and UE 1102,configure according to one aspect of the present disclosure. Similar tothe 2-step simplified procedure from FIG. 11A, at time 1103, UE 1102sends a combined random access request message that includes the randomaccess request and initial PUSCH transmission. At time 1106, eNB 1101,having received the random access request with the initial PUSCHinformation, sends a random access response message which simplyacknowledges the random access request of the combined message at time1103, such that re-transmissions and power ramp-ups can be stopped. Attime 1107, eNB 1101 sends the additional connection setup information.Thus, the potential latency between Msg 3 and Msg 4 is addressed bysplitting the messages from eNB 1101 in response to the combined randomaccess request message.

It should be noted that, at least for some scenarios (e.g., handover),the 2-step simplified RACH procedure illustrated in FIG. 11A issufficient, as the material of Msg 4, combined into the second messageat 1104 may not be necessary, which would prevent the latency issue fromarising. However, in scenarios in which the latency between Msg 3 andMsg 4 would be large, it may be more efficient to opt for the 3-stepsimplified RACH procedure illustrated in FIG. 11B. In still furtheraspects, it may be desirable to have a single simplified alternativeRACH procedure for all scenarios.

In various aspects of the present disclosure, as illustrated in FIGS.11A and 11B, the combined random access request message at 1103 is sentby UE 1102 containing at least the UE identifier (UE ID), such as, forexample, the international mobile station equipment identity (IMEI)number. Additionally, UE 1102 may derive a PRACH group and a sequencewithin the group for transmission of the combined random access request.This derivation can be purely random or, alternatively, based on variousinformation, such as the UE ID, which may be embedded in the randomaccess request. Moreover, in additional aspects, the cyclic redundancycheck (CRC) of the combined message should not be scrambled using UE ID,as eNB 1101 would not yet have access to the UE ID.

Additional aspects may also provide more specific information in thecombined random access response message send by eNB 1101 at 1104. Forexample, eNB 1101 may respond with the cell radio network temporaryidentifier (C-RNTI) assignment, etc. Depending on the latency and thetype of RACH procedure (e.g., initial access vs. handover), the latencybetween step 1 and step 2 can be large (e.g., for initial access, andcan be tens of milliseconds) or small (e.g., for handover).

In various aspects of the present disclosure, the second message (e.g.,the combined random access response message) of the simplified 2-StepRACH process may be transmitted as a unicast or multicast transmission.Unicast transmissions may be less overhead-efficient compared withmulti-cast. If transmitted as a unicast message, the UE IDs may be usedto scramble the entire combined random access response message. Inmulticast, however, the message will contain information for more thanone UE. UE IDs may, therefore, be part of the payload in the message. Toimprove security of the UE-specific information in the multi-cast, theportion of the message containing the UE-specific information may bescrambled with the UE ID corresponding to the UE to which theinformation is directed.

In a multicast transmission aspect, the combined random access responsemessage may be organized into two portions: a common information portionthat includes information that may be shared by multiple UEs, and theUE-specific portion, which includes sets of UE-specific informationarranged by the UE to which the information relates. FIG. 12 is a blockdiagram illustrating a combined random access response message 1200 froma base station configured according to one aspect of the presentdisclosure. Combined random access response message 1200 includes commoninformation portion 1201, which contains various information that may becommon to two or more UEs which are associated with a RACH procedure atthe base station, and UE-specific information portion 1202, whichcontains various UE-specific information. For example, as illustrated inFIG. 12, UE-specific information portion 1202 includes specificinformation for UE_1 1202-1, UE_2 1202-2, through UE_K 1202-K. As notedabove, each of the individual UE-specific information subsections1202-1-1202-K, may be scrambled with the associated UE ID. Thus, anotherUE may not be capable of viewing relevant UE-specific information aboutanother UE.

It should be noted that in the various aspects of the presentdisclosure, the UE will both transmit the combined request message andlook for the response message from the eNB in both guaranteed andnon-guaranteed subframes.

Besides regular PRACH subframes, which may be transmitted and/orreceived in guaranteed and non-guaranteed subframes, various aspects ofthe present disclosure also provide for on-demand PRACH allocations thatmay be assigned by an eNB to a UE to expedite the RACH procedure, suchas during handover. FIGS. 13A and 13B are functional block diagrams thatillustrate example blocks executed to implement one aspect of thepresent disclosure. At block 1300, a base station generates an expeditedrandom access allocation. The expedited random access allocationinstructs the UE to begin the RACH process without first performing aCCA check on the subframe. At block 1301, the base station transmits theexpedited random access allocation to the UE either in a CCA subframe(cleared non-guaranteed) or a non-CCA subframe (guaranteed). At block1302, a UE receive the expedited random access allocation from the basestation. At block 1303, the UE transmits a random access request in anext available subframe without determining whether the next availablesubframe is a random access designated subframe. Thus, the UE respondsthe demand by starting PRACH in a close-by, and what could be anon-regular PRACH subframe.

Typical random access response grants in LTE contain the followinginformation fields: a 1-bit hopping flag, a 10-bit fixed size resourceblock assignment, a 4-bit truncated modulation and coding scheme (MCS),a 3-bit transmit power control (TPC) command for scheduled PUSCH, a1-bit uplink delay, a 1-bit CSI request, and additional information,such as the RRC connection setup information. In considering LTE/LTE-Adeployments with unlicensed spectrum, the random access request grantmay continue to include most of this information with only slightmodifications from LTE implementations. For example, the hopping flagmay not be necessary, depending on the uplink multiplexing structure.The fixed size resource block assignment may be simplified and/orre-interpreted, for example, to indicate the amount of decimation (e.g.,number of combs) and frequency offset in the frequency domain, and/ornumber of symbols. The LTE/LTE-A RAR with unlicensed spectrum grant maystill have the truncated MCS, though the number of bits may be reducedfrom the standard 4-bit field. The TPC command for scheduled PUSCH isstill included. The other RAR grant information, such as the uplinkdelay, CSI request, and the additional grant information may also beincluded in the LTE/LTE-A RAR with unlicensed spectrum grantinformation.

It should be noted that, in general aspects of the present disclosure, aUE configured for transmission over at least unlicensed spectrumgenerates uplink signals and determines non-CCA subframes over which totransmit at least some of those generated uplink signals to a servingbase station. The serving base, which is also configured forcommunication over at least unlicensed spectrum, identifies non-CCAsubframes over which it may receive uplink signals and receives any suchuplink signals in the non-CCA subframes over the unlicensed band.

FIG. 14A is a functional block diagram illustrating example blocksexecuted to implement one aspect of the present disclosure. At block1400, a UE generates one or more uplink signals for transmission to aserving base station. The UE of the illustrated aspect is configured totransmit communication signals to a serving base station over at leastunlicensed spectrum and to receive communication signals from theserving base station. At block 1401, the UE determines a non-CCAsubframe for transmission of at least one of the generated uplinksignals. At block 1402, the UE transmits the uplink signals in thenon-CCA subframe over an unlicensed band.

FIG. 14B is a functional block diagram illustrating example blocksexecuted to implement one aspect of the present disclosure. At block1403, the serving base station identifies a non-CCA subframe forreception of at least one uplink signal. The serving base station of theaspect illustrated in FIG. 14B may serve the UE performing the blocksillustrated in FIG. 14A. The serving base station would be configuredfor communication over at least unlicensed spectrum. At block 1404, theserving base station receives one or more uplink signals from a UE inthe non-CCA subframe over an unlicensed band.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

The functional blocks and modules in FIGS. 8A-8B, 13A-13B, and 14A-14Bmay comprise processors, electronics devices, hardware devices,electronics components, logical circuits, memories, software codes,firmware codes, etc., or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure. Skilled artisans will also readilyrecognize that the order or combination of components, methods, orinteractions that are described herein are merely examples and that thecomponents, methods, or interactions of the various aspects of thepresent disclosure may be combined or performed in ways other than thoseillustrated and described herein.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another.Computer-readable storage media may be any available media that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, such computer-readable media can compriseRAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic diskstorage or other magnetic storage devices, or any other medium that canbe used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, a connection may be properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, or digital subscriber line (DSL), thenthe coaxial cable, fiber optic cable, twisted pair, or DSL, are includedin the definition of medium. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), floppy disk and blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

As used herein, including in the claims, the term “and/or,” when used ina list of two or more items, means that any one of the listed items canbe employed by itself, or any combination of two or more of the listeditems can be employed. For example, if a composition is described ascontaining components A, B, and/or C, the composition can contain Aalone; B alone; C alone; A and B in combination; A and C in combination;B and C in combination; or A, B, and C in combination. Also, as usedherein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of” indicates a disjunctive list such that,for example, a list of “at least one of A, B, or C” means A or B or C orAB or AC or BC or ABC (i.e., A and B and C).

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method of wireless communication, comprising:generating, at a user equipment (UE), one or more uplink signals fortransmission to a serving base station, wherein the UE is configured totransmit communication signals to the serving base station over at leastan unlicensed spectrum and receive communication signals from theserving base station; determining, by the UE, a non-clear channelassessment (non-CCA) subframe and a CCA subframe, wherein the non-CCAsubframe is for transmission of at least one of the one or more uplinksignals; and transmitting, by the UE over an unlicensed band, the atleast one of the one or more uplink signals in the non-CCA subframe. 2.The method of claim 1, wherein configuration of the non-CCA subframe isassociated with a duration and a periodicity, and a ratio between theduration and the periodicity is no more than 5%.
 3. The method of claim1, wherein the communication signals received from the serving basestation are orthogonal division multiple access (OFDMA) signals.
 4. Themethod of claim 1, wherein the one or more uplink signals include atleast one of: a sounding reference signal (SRS); a scheduling request(SR); channel state information (CSI) feedback; uplink discoverysignals; physical random access channel (PRACH); or physical uplinkshared channel.
 5. The method of claim 1, further including: detecting,by the UE, a clear CCA in the CCA subframe; and transmitting, by the UE,at least one other of the one or more uplink signals in the CCA subframein response to detecting the clear CCA, wherein the transmitting occursbefore expiration of a predetermined time from the detecting.
 6. Themethod of claim 1, wherein an offset of the non-CCA subframe fortransmitting the one or more uplink signals is a function of anotheroffset of another non-CCA subframe for reception of one or more downlinksignals from the serving base station.
 7. The method of claim 1, furtherincluding: receiving a downlink transmission in a non-CCA subframe fromthe serving base station, wherein the transmitting the at least one ofthe one or more uplink signals is in response to the receiving thedownlink transmission.
 8. The method of claim 1, further including:determining a transmission state of the serving base station; anddetermining whether to perform a re-transmission of at least one of theone or more uplink signals in response to the determined transmissionstate.
 9. The method of claim 8, wherein the at least one of the one ormore uplink signals is a random access request and the transmissionstate includes at least one of: a cleared-to-transmit state, or anon-cleared-to-transmit state, and in response to the transmissionstate, one of: suspending re-transmission of the random access requestwhen the transmission state indicates the serving base station is notcleared of sending a random access response; or re-transmitting therandom access request when the transmission state indicates the servingbase station is cleared of sending the random access response.
 10. Themethod of claim 8, wherein the determining the transmission stateincludes: monitoring, by the UE, for one or more reference signalstransmitted by the serving base station; determining anot-cleared-to-transmit transmission state when the UE fails to detectthe one or more reference signals; determining a cleared-to-transmittransmission state when the UE detects the one or more referencesignals; and determining a cleared-to-transmit transmission state whenthe UE detects a non-CCA subframe.
 11. The method of claim 1, furtherincluding: determining a first offset for a first non-CCA subframe; andadjusting to a second offset, different from the first offset, for asecond non-CCA subframe, in response to an idle duration between thefirst non-CCA subframe and the second non-CCA subframe wherein the idleduration at least meets a threshold duration.
 12. The method of claim 1,wherein the at least one of the one or more uplink signals includes amodified random access request, wherein the modified random accessrequest is a function of an identifier of the UE.
 13. The method ofclaim 12, further including receiving a modified random access responsemessage, wherein the modified random access response message includes afirst portion of information common to the UE and one or more additionalUEs and one or more second portions of information, wherein each of theone or more second portions of information includes UE-specificinformation.
 14. A method of wireless communication, comprising:identifying, by a serving base station configured for communication overat least an unlicensed spectrum, a non-clear channel assessment(non-CCA) subframe and a CCA subframe, wherein the non-CCA subframe isfor reception of at least one uplink signal; and receiving, at theserving base station, over an unlicensed band one or more uplink signalsfrom a user equipment (UE) in the non-CCA subframe.
 15. The method ofclaim 14, wherein configuration of the non-CCA subframe is associatedwith a duration and a periodicity, and a ratio between the duration andthe periodicity is no more than 5%.
 16. The method of claim 14, whereinthe one or more uplink signals include at least one of: a soundingreference signal (SRS); a scheduling request (SR); channel stateinformation (CSI) feedback; uplink discovery signals; physical randomaccess channel (PRACH); or physical uplink shared channel.
 17. Themethod of claim 14, further including identifying an offset of thenon-CCA subframe for at least one UE, where the offset is a function ofanother offset of another non-CCA subframe for transmitting one or moredownlink signals from the serving base station.
 18. The method of claim14, further including: determining a transmission state of the servingbase station; and determining whether or not to receive are-transmission of at least one of the one or more uplink signals inresponse to the transmission state.
 19. The method of claim 18, whereinat least one of the one or more uplink signals is a random accessrequest and the transmission state includes at least one of acleared-to-transmit state, or a non-cleared-to-transmit state, and inresponse to the transmission state, determining one of: suspendingreceiving of the re-transmitted random access request when thetransmission state indicates the serving base station is not cleared ofsending a random access response; or receiving the re-transmitted randomaccess request when the transmission state indicates the serving basestation is cleared of sending the random access response.
 20. The methodof claim 18, wherein the determining the transmission state includes:determining a not-cleared-to-transmit transmission state when theserving base station does not transmit one or more reference signals;determining a cleared-to-transmit transmission state when the servingbase station transmits one or more reference signals; and determining acleared-to-transmit transmission state when the serving base stationstransmits in a non-CCA subframe.
 21. The method of claim 14, furtherincluding: determining a first offset for a first non-CCA subframe forthe UE; and adjusting to a second offset, different from the firstoffset, for a second non-CCA subframe, in response to an idle durationat the UE between the first non-CCA subframe and the second non-CCAsubframe, wherein the idle duration at least meets a threshold duration.22. The method of claim 14, wherein the one or more uplink signalsinclude a modified random access request, wherein the modified randomaccess request is a function of an identifier of the UE.
 23. The methodof claim 22, further including transmitting a modified random accessresponse message, wherein the modified random access response messageincludes a first portion of information common to the UE and one or moreadditional UEs and one or more second portions of information, whereineach of the one or more second portions of information includesUE-specific information.
 24. An apparatus configured for wirelesscommunication, comprising: at least one processor; and a memory coupledto the at least one processor, wherein the at least one processor isconfigured: to generate, at a user equipment (UE), one or more uplinksignals for transmission to a serving base station, wherein the UE isconfigured to transmit communication signals to the serving base stationover at least an unlicensed spectrum and receive communication signalsfrom the serving base station; to determine, by the UE, a non-clearchannel assessment (non-CCA) subframe and a CCA subframe, wherein thenon-CCA subframe is for transmission of at least one of the one or moreuplink signals; and to transmit, by the UE over an unlicensed band, theat least one of the one or more uplink signals in the non-CCA subframe.25. The apparatus of claim 24, wherein the at least one processor isfurther configured: to detect, by the UE, a clear CCA in the CCAsubframe; and to transmit, by the UE, at least one other of the one ormore uplink signals in the CCA subframe in response to detecting theclear CCA, wherein the transmitting occurs before expiration of apredetermined time from the detecting.
 26. The apparatus of claim 24,wherein an offset of the non-CCA subframe for transmitting the one ormore uplink signals is a function of another offset of another non-CCAsubframe for reception of one or more downlink signals from the servingbase station.
 27. The apparatus of claim 24, wherein the at least oneprocessor is further configured: to determine a transmission state ofthe serving base station; and to determine whether to perform are-transmission of at least one of the one or more uplink signals inresponse to the determined transmission state.
 28. An apparatusconfigured for wireless communication, comprising: at least oneprocessor; and a memory coupled to the at least one processor, whereinthe at least one processor is configured: to identify, by a serving basestation configured for communication over at least an unlicensedspectrum, a non-clear channel assessment (non-CCA) subframe and a CCAsubframe, wherein the non-CCA subframe is for reception of at least oneuplink signal; and to receive, at the serving base station, over anunlicensed band one or more uplink signals from a user equipment (UE) inthe non-CCA subframe.
 29. The apparatus of claim 28, wherein the atleast one processor is further configured: to identify an offset of thenon-CCA subframe for at least one UE, where the offset is a function ofanother offset of another non-CCA subframe for transmitting one or moredownlink signals from the serving base station.
 30. The apparatus ofclaim 28, wherein the at least one processor is further configured: todetermine a transmission state of the serving base station; and todetermine whether or not to receive a re-transmission of at least one ofthe one or more uplink signals in response to the transmission state.